To accommodate multiple application demands such as service separation and in-band management, network multi-topology technologies emerge as required. One physical network may be divided into multiple logical networks, that is, multiple logical topologies. How to transmit data in a multi-topology network is a problem to be solved in the network topology technologies.
The existing multi-topology technology defines a way for selecting an RIB/FIB (Routing Information Base/Forward Information Base, routing information base/forwarding information base) in the multi-topology network, that is, defines packet forwarding within multiple logical topologies in a physical topology network. If the multi-topology network has two topologies, topology 1 and topology 2, an ingress node (Ingress node) in the multi-topology network has two RIBs/FIBs, respectively recording routing information in topology 1 and topology 2 and both for directing forwarding. If a packet is initiated by the Ingress node in the multi-topology network, a topology whose RIB/FIB is to be selected may be specified on the Ingress node, and the packet is forwarded according to the selected RIB/FIB of a downlink topology.
The prior art only defines how to perform data forwarding in a multi-topology network in the case where a packet is initiated from the ingress node in the multi-topology network. However, before the introduction of the multi-topology network, a physical topology and a logical topology are combined into one. This combined topology is a default topology network under the concept of the multi-topology network. A practical transport network is formed by a default topology network and a multi-topology network. If the packet is initiated from the default topology network, and duplicate destination addresses exist, after receiving the packet, the ingress node in the multi-topology network does not know the topology whose RIB/FIB is to be selected due to the duplicate destination addresses, and consequently fails to correctly select a route for the packet.